1. Field of the Invention
The present invention relates to an image communication apparatus, an image communication system incorporating the image communication apparatus and an image communication method for use in the above image communication apparatus or in the above image communication system and more particularly to the image communication apparatus, image communication system and image communication method that can be suitably employed in image communication through an IP (Internet Protocol) network.
2. Description of the Related Art
In conventional image communication systems, after an image communication apparatus to which an image is to be transmitted is designated by, for example, a telephone number of a facsimile serving as the image communication apparatus to which the image is to be transmitted, the image is transmitted through a telephone network to the designated facsimile. In recent years, in addition to transmission and receipt of images through the telephone network, the transmission and receipt of images through a computer network by designating an image communication apparatus to which the image is to be transmitted using a network address on a computer network such as the Internet and/or intranet are becoming widespread.
The above conventional image communication system is provided with a gatekeeper which enables an image communication apparatus on a sender side to acquire a network address assigned to an image communication apparatus on a receiver side. The gatekeeper is adapted to store correspondence between the telephone number and the network address and, in response to an inquiry from the image communication apparatus on the sender side, to notify the image communication apparatus on the sender side of the network address of the image communication apparatus on the receiver side.
However, according to the ITU-T (International Telecommunication Union-Telecommunication) Recommendation H.323, all that the gatekeeper can do is to store only one sort of correspondence between a telephone number and a network address or between a plurality of telephone numbers and a plurality of network addresses, that is, is prohibited from storing a plurality of sorts of correspondences, to provide the network address corresponding to an inquired telephone number according to the above correspondence. Therefore, for example, either of an outside telephone number or an inside telephone number can be used in a fixed manner, however, it is impossible to selectively use both the outside and inside telephone numbers in order to acquire the network address common thereto.